Musannaf Ibn Abi Shayba 13:1386

Abu Bakr narrated to us, he said: Waki’ narrated to us, from Abu Shabib, from Ikrimah, from Ibn Abbas, that Umar had a slave of his, whose kunya was Abu Umayyah, enter into a contract of manumission (kitabah). He came to him with his installment when it arrived, and he (Umar) said: "O Abu Umayyah, seek help with it for your manumission contract." He said: "O Commander of the Faithful, if you were to leave it until it is the final installment?" He said: "I fear that I will not reach that." Then he recited: "And give them from the wealth of Allah which He has given you." Ikrimah said: "And it was the first installment paid in Islam."